Amazon Reorder Point Calculator
Your reorder point is the inventory level at which the next purchase order has to be placed, and it equals the units you will sell during the entire replenishment lead time plus a safety stock buffer. On Amazon that lead time has three stages, not two: production at the factory, transit to the country of sale, and Amazon receiving, because units are not sellable until a fulfillment center has checked them in. This calculator adds those stages, converts them into units at your current sales rate, adds safety stock expressed in days of cover, and tells you how many days remain before your inventory reaches that trigger level. Enter your own numbers below; the fields load with a worked example already filled in.
Calculate your reorder point
How the reorder point calculation works
The whole method rests on one idea: the inventory you hold today has to survive every day between placing an order and that order becoming sellable, with something left over for the days that go wrong.
- Total lead time = production days + transit days + Amazon receiving days. Most reorder formulas stop after the first two, which is where the error creeps in.
- Demand during lead time = average daily unit sales × total lead time. This is the number of units you will sell while the replacement order is being made, shipped, and checked in, and it is the bare minimum you must be holding on the day you place the order.
- Safety stock = average daily unit sales × safety days of cover. Holding the buffer in days rather than units means it rescales on its own as the product grows, so a SKU that doubles in sales does not silently end up with half the protection it had.
- Reorder point = demand during lead time + safety stock. When sellable inventory falls to this figure, the purchase order goes out.
- Current days of cover = sellable inventory ÷ daily sales, and days until the reorder point = (sellable inventory − reorder point) ÷ daily sales. The second figure is the one to put in a calendar reminder.
- Suggested order quantity = daily sales × 90, a reference size for a roughly one-quarter cycle. Treat it as a starting point and then check it against storage cost and cash, not as the answer.
The receiving stage is the part that distinguishes an Amazon reorder point from a textbook one. A container that arrives at a fulfillment center is not inventory yet. It has to be booked in, unloaded, scanned, and released to sellable status, and that stage regularly runs into days and stretches further when the network is busy in the run-up to peak. If your model assumes goods are available the moment they are delivered, you have quietly removed a week or two of cover from the calculation, and the shortfall lands in exactly the week the shipment was supposed to save you.
Expressing safety stock in days of cover rather than in a fixed unit count is the second practical improvement. A buffer of 800 units sounds concrete and means nothing on its own: it is five weeks of protection at 25 units a day and nine days at 90. Days of cover states the thing you actually care about, which is how long the buffer lasts, and it stays correct as the product scales. Widen it when demand is volatile, when you have a single supplier with no backup, or when transit is long; narrow it when you can air-freight a top-up in two weeks.
The reason the reorder point sits above zero by design is that a stockout on Amazon costs more than the missed orders. Sales velocity is a major input to organic rank, so a listing that goes to zero loses position and then has to buy that position back with advertising once stock returns. The cost of being early on a purchase order is storage fees and tied-up cash, both of which you can measure with the storage and aged inventory calculator. The cost of being late is a rank recovery you cannot schedule. Those two risks are not symmetrical, which is why the buffer exists.
One seasonal adjustment matters more than any other. This formula is linear in daily sales, so every input scales with the rate you enter. Before running it for a fourth-quarter cycle, raise average daily unit sales to the rate you expect during the weeks the stock will actually sell rather than the trailing average from a quiet summer month. A SKU running 40 units a day in August that will run 90 in November needs a reorder point built on 90. The timing checkpoints and the cutoffs to work back from are in the Q4 2026 prep playbook and the seller calendar. Finally, remember that the order quantity you place also has to be paid for at landed cost, so confirm the cash requirement with the landed cost calculator before you sign the proforma invoice.
Worked example: a SKU selling 40 units a day on an 85 day lead time
These are the values the calculator loads with, so you can see the method and the widget agree. Figures are illustrative.
- 40 units a day, production 45 days, transit 30 days, Amazon receiving 10 days, safety stock 21 days of cover, current sellable inventory 5,200 units.
- Total lead time: 45 + 30 + 10 = 85 days.
- Demand during lead time: 40 × 85 = 3,400 units.
- Safety stock: 40 × 21 = 840 units.
- Reorder point: 3,400 + 840 = 4,240 units.
- Current days of cover: 5,200 ÷ 40 = 130 days. Days until the reorder point: (5,200 − 4,240) ÷ 40 = 24 days.
Read the last two lines together. This SKU has over four months of stock and still has only 24 days before the purchase order has to go out, because 85 of those 130 days are already committed to the replenishment cycle. A suggested 90 day order at this rate is 3,600 units.
Frequently asked questions
What is a reorder point and why is it not zero?
The reorder point is the inventory level at which you place the next purchase order, not the level at which you run out. It sits above zero because the replacement units take months to arrive, and it sits above the lead time demand as well because demand and lead times both vary. The gap between those two is the safety stock.
Why does this calculator include an Amazon receiving stage?
Because units are not sellable the day the truck arrives. A shipment has to be checked in, scanned, and made available before it counts as inventory, and that stage routinely takes days and can take longer around peak. Standard reorder formulas assume goods are available on delivery, which is exactly the assumption that produces stockouts in the week the container lands.
How much safety stock should I hold?
Expressing it in days of cover is easier to reason about than a fixed unit buffer, because it rescales automatically as sales grow. Two to three weeks is a common starting point for a stable SKU with a reliable supplier. Widen it for volatile demand, a single-source supplier, long ocean transit, or the fourth quarter, and narrow it for a product with a short domestic lead time.
What does a stockout actually cost on Amazon?
More than the lost orders. A listing that goes out of stock loses sales velocity, and sales velocity is what holds organic rank, so the recovery period after restocking usually costs more than the outage itself in advertising spend to rebuild position. That asymmetry is the reason the reorder point is set above zero rather than at it.
Should I raise daily sales before running this for Q4?
Yes. The formula is linear in daily sales, so a fourth quarter that runs at twice your baseline doubles both the lead time demand and the safety stock. Run the calculation with the daily rate you expect during the period the stock will actually sell, not the trailing average from a quiet month, or the reorder point will be set for a season you are not in.
Sources
- Amazon Seller Central: inventory planning, restock recommendations, and shipment receiving status (primary source for your current quantities and recent check-in times).
- Seller Signal analysis. All example figures above are illustrative planning values, not current published rates or service levels.